In a vehicle, a transmission of changing rotation of power transmitted from an engine and transmitting the resultant power to driving wheels is mounted. As the transmission, in recent years, an automatic transmission for automatically changing speed without a gear shift operation of the driver is often used. The automatic transmission is provided so that the gear can be shifted by a control apparatus for controlling the automatic transmission. Such an apparatus for controlling the gear shift of the automatic transmission performs a gear shift control on the automatic transmission by selecting a proper gear in accordance with driving conditions of a vehicle. In the case of selecting a proper gear in accordance with driving conditions of a vehicle, for example, a gear at which the fuel consumption is minimum in a present travel state is selected and the gear of the automatic transmission is shifted to the selected gear. It can improve fuel consumption at the time of travel of a vehicle.
However, in the case of performing the gear shift by selecting a gear at which the fuel consumption is the minimum as described above, the selected gear frequently changes according to an operation of an accelerator pedal or the like. Since the gear shift is frequently performed, there is the case that drivability deteriorates. Consequently, there is a conventional gear shift control apparatus for an automatic transmission, which suppresses frequent gear shifts in the gear shift control on the automatic transmission for the purpose of improvement in fuel consumption.
For example, a control apparatus for an automatic transmission described in patent literature 1 calculates a gear at which the fuel consumption becomes the minimum on the basis of an operation amount of an accelerator pedal and travel speed of a vehicle, does not shift the gear in a case where a difference between a fuel consumption in the present gear and a fuel consumption in the calculated gear is less than a predetermined threshold, and shifts the gear in a case where the difference of the fuel consumptions is equal to or larger than the predetermined threshold. With the technique, the gear can be shifted to the gear at which the fuel consumption can be reduced, and frequent gear shifts can be suppressed.